JavaFX - Call "updateMessage" for TextArea from background Task - Two problems found - javafx

I am having two problems when trying to use "updateMessage" in a JavaFX task.
Issue #1
seems to be a known behavior, but I am not yet sure how exactly I can workaround it.This one is not (yet) critical to me.
The problem is that not all the updates I am performing in a background Task are displayed in the UI (at least the UI does not hang/freezes anymore, which was my initial issue).
My Code of the UI part:
TextArea console = new TextArea();
Button button01 = new Button("Start");
button01.setOnAction(new EventHandler() {
#Override
public void handle(Event event) {
if (ms.getState() == State.READY) {
ms.messageProperty().addListener(new ChangeListener<String>() {
#Override
public void changed(ObservableValue<? extends String> observable,
String oldValue, String newValue) {
console.appendText(newValue+"\n");
}
});
ms.start();
}
}
});
My Service:
public class MyService extends Service<Object> {
#Override
protected Task createTask() {
//here we use "MyTask" first to show problem #1
MyTask ct = new MyTask();
//here we use "MyTask2" first to show problem #2
// MyTask2 ct = new MyTask2();
try {
ct.call();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("MyService end");
return ct;
}
}
My Task (#1)
public class MyTask extends Task<Object> {
#Override
public EventHandler<WorkerStateEvent> call() {
System.out.println("call() is called");
if (Thread.currentThread().getName().equals("JavaFX Application Thread")){//yes, this might not be right, but if I do not do this, my stuff is executed twice because "call()" is called twice, but the textarea area is just updated in the second run (the non javafx application thread).
return null;
} else{
//actually here I want to do some 'heavy' stuff in the background
//and many things of this heavy stuff should be displayed / logged within the UI
//but very likely (hopefully) new messages (updateMessage) will not be send as fast as in the following loop
for (int i=0;i<10000000;i++){
updateMessage("This is update number'"+i+"' from the background thread");
}
Platform.runLater(new Runnable() {
#Override
public void run() {
try{
//here is the chance to get back to the view
}finally{
}
}
});
return null;
}
}
This basically works, but not every single loop is displayed in the UI.
How do I (correctly) make sure every loop is displayed?
Screenshot: Messages are displayed but not for every loop
Issue #2
Currently blocks my attempt to bring my little text-based game into a JavaFX application.
The main problem is that I am able to call "updateMessage" from the Task directly (see above), but not from a another (sub-)class which I would need to bring all message updates from my game (each message describes the progress of the game) to the UI.
The Task I use (Task #2):
public class MyTask2 extends Task<Object> {
#Override
public EventHandler<WorkerStateEvent> call() {
// ...
UITools myTools = new UITools();
myTools.logToUITest("Just one simple message");
// ...
Platform.runLater(new Runnable() {
#Override
public void run() {
try{
//here is the chance to get back to the view
}finally{
}
}
});
return null;
}
and the (sub-)class that I want to use to do the updateMessage (actually in my little game there would be even more classes that are called during the game and almost all of them trigger an update/message).
public class UITools {
public void logToUITest(String message){
updateMessage(message);
//how to allow 'updateMessage' from the Task to be executed from here?
}
This already results in "The method updateMessage(String) is undefined...".
How could I make it possible to call the updateMessage outside of the Task itself?

updateMessage() can only be called from within the call() method of a Task. It's a constraint imposed by the design of the Task class.
The missed message updates are due to the fact that there are too many updates and not all of them are forwarded to the event queue. Try to reduce the number of updates or sleep for a little while to separate them out in time

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How to know FirebaseRecyclerAdapter query is zero or not, exist or not

How to know FirebaseRecyclerAdapter query is zero or not, exist or not
I find some instructions on
https://github.com/firebase/FirebaseUI-Android/tree/master/database
it says:
Data and error events
When using the FirebaseRecyclerAdapter you may
want to perform some action every time data changes or when there is
an error. To do this, override the onDataChanged() and onError()
methods of the adapter:
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// ...
#Override
public void onDataChanged() {
// Called each time there is a new data snapshot. You may want to use this method
// to hide a loading spinner or check for the "no documents" state and update your UI.
// ...
}
#Override
public void onError(DatabaseError e) {
// Called when there is an error getting data. You may want to update
// your UI to display an error message to the user.
// ...
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};
When I tried to use as follow:
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{
#Override
public void onDataChanged(DataSnapshot dataSnapshot)
{
// Called each time there is a new data snapshot. You may want to use this method
// to hide a loading spinner or check for the "no documents" state and update your UI.
// ...
if (dataSnapshot.exists())
{
Log.d(TAG,"data exists");
}
else
{
Log.d(TAG,"No data exists");
}
}
#NonNull
#Override
public PlaceViewHolder onCreateViewHolder(#NonNull ViewGroup viewGroup, int i)
{
Error message is:
Method does not override method from its superclass
So how can I solve this problem, Thank you.
I found the answer from another page:
https://www.programcreek.com/java-api-examples/?api=com.firebase.ui.database.FirebaseRecyclerAdapter
#Override
public void onDataChanged()
{
// Called each time there is a new data snapshot. You may want to use this method
// to hide a loading spinner or check for the "no documents" state and update your UI.
// ...
if (getItemCount() == 0)
{
Log.d(TAG,"No data exists");
}
else
{
Log.d(TAG,"data exists");
}
}

JavaFX Task updateValue throws IllegalStateException: Not on FX application thread

I have a simple application with a single JavaFX window. I'm sending in data to an Azure IoTHub inside a for loop. This for loop is in a JavaFX Task, and the for loop has a small delay (Thread.sleep(300)) so progress can be shown on the UI. I have 2 labels I want to update during the data transmission, always showing the latest sent in data. I have the following helper class for this:
public class DataHelper {
private StringProperty date = new SimpleStringProperty();
private StringProperty count = new SimpleStringProperty();
public DataHelper() {
}
public DataHelper(String date, String count) {
this.date.setValue(date);
this.count.setValue(count);
}
//getters and setters
}
And here is my sendErrorsToHub method inside my UI controller class:
private void sendErrorsToHub(List<TruckErrorForCloud> toCloud) {
DataHelper dataHelper = new DataHelper("", "");
Task task = new Task<DataHelper>() {
#Override
public DataHelper call() {
try {
int i = 0;
for (TruckErrorForCloud error : toCloud) {
Thread.sleep(300);
i++;
String strMessage = Utility.toPrettyJson(null, error);
if (strMessage != null) {
Message msg = new Message(strMessage);
msg.setMessageId(java.util.UUID.randomUUID().toString());
client.sendEventAsync(msg, null, null);
}
updateProgress(i, toCloud.size());
DataHelper dh = new DataHelper(error.getErrorTimeStamp().substring(0, error.getErrorTimeStamp().length() - 9),
String.valueOf(error.getCount()));
updateValue(dh);
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void updateValue(DataHelper value) {
super.updateValue(value);
dataHelper.setDate(value.getDate());
dataHelper.setCount(value.getCount());
}
//succeeded method omitted
};
dateValue.textProperty().bind(dataHelper.dateProperty());
countValue.textProperty().bind(dataHelper.countProperty());
progressBar.progressProperty().bind(task.progressProperty());
new Thread(task).start();
}
When I run the application, I constantly get IllegalStateException: Not on FX application threadexceptions, inside the updateValue method. As far as I understand the documentation, the whole point of the updateValue method, that it runs on the Application thread, and it can be used to pass a custom object, which can be used to update the UI.
What am I doing wrong then?
The bottom of the stacktrace with my classes is the following:
at eu.mantis.still_rca_simulator.gui.DataHelper.setDate(DataHelper.java:28)
at eu.mantis.still_rca_simulator.gui.GuiController$1.updateValue(GuiController.java:166)
at eu.mantis.still_rca_simulator.gui.GuiController$1.call(GuiController.java:155)
at eu.mantis.still_rca_simulator.gui.GuiController$1.call(GuiController.java:138)
(138 is the line Task task = new Task(), 155 updateValue(dh);, 166 dataHelper.setDate(value.getDate());)
updateValue does not automatically run on the application thread and it's not necessary to run it on the application thread since it takes care of updating the value property of Task on the application thread.
Your code in the overridden version updateValue executes logic on the background thread that needs to be run on the application thread though:
dataHelper.setDate(value.getDate());
dataHelper.setCount(value.getCount());
The bindings result in the text properties being updated from the background thread since the above code runs on the background thread.
In this case I recommend using a immutable DataHelper class and updating the ui using a listener to the value property:
Remove the updateValue override and the dataHelper local variable, initialize the gui with empty strings, if necessary, declare task as Task<DataHelper> task and do the following to update the gui:
task.valueProperty().addListener((o, oldValue, newValue) -> {
if (newValue != null) {
dateValue.setText(newValue.getDate());
countValue.setText(newValue.getCount());
}
});
You may also use Platform.runLater for those updates, since they don't happen frequently enough to result in issues that could be the result of using Platform.runLater too frequently.

How to Post a runnable to a View that invalidates the View sometimes doesn't work

I been fighting an odd issue these last few days. I have a custom ExpandableListAdapter where each row contains an ImageView, among other things. I have a class that handles the asynchronous loading of images from the multitude of places they may reside (disk cache, app data, remote server, etc). In my adapter's getView method I delegate the responsibility of returning a View to the list Item itself (I have multiple row types for my group list). I request the image load as follows:
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#Override
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thumb.setImageBitmap(b);
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JavaFX auto-scroll auto-update text

Newbie question about JavaFX that I haven't been able to answer, despite knowing it must be pretty simple to do and not finding any resources on it anywhere I've looked (tutorials, many of the Oracle online docs, articles, the well-known JavaFX bloggers, etc.)
I'm developing a command line (script) running application and I have successfully gotten output (via ProcessBuilder) from the script that I can display in an ongoing manner, as things happen on the command line. That is, I can do System.out.println(line); all day long, showing the output in the console, which simply returns output from an input stream returned by the 'myProcess' that's running, created like this:
BufferedReader bri = new BufferedReader(new InputStreamReader(myProcess.getInputStream()))
So I am able to see all the output coming back from the script.
I'd like to set-up a JavaFX TextArea or ScrollPane or, not sure what, to display this output text (there's a lot of it, like several thousand lines) as an ongoing 'progress' of what's taking place in the script, as it happens. I have a Scene, I have buttons and get input from this scene to start the script running, but now I'd like to show the result of clicking the button "RUN THIS SCRIPT", so to speak.
I assume I need to create a TextArea as described here or perhaps a TextBuilder would be useful to begin making it. Not sure.
I need a bit of help in how to setup the binding or auto-scroll/auto-update part of this.
Can someone provide me a place to start, to do this with JavaFX? I'd rather not use Swing.
(I'm using JavaFX 2.2, JDK 1.7u7, all the latest stuff, and yes, this is an FXML app--so doing it that way would be preferred.)
UPDATE: Sergey Grinev's answer was very helpful in the binding part. But here is some more detail on what I mean when I ask for "a bit of help in how to setup" -- basically, I need to return control to the main Scene to allow the user to Cancel the script, or to otherwise monitor what's going on. So I'd like to "spawn" the process that runs that script (that is, have some kind of 'free running process'), but still get the output from it. (I wasn't very clear on that in my initial question.)
The technique I'm using here (see below) is to do a waitFor on the process, but of course this means the dialog/Scene is 'hung' while the script executes. I'd like to gain control back, but how do I pass the 'p' (Process) to some other controller piece (or alternatively, simply kick off that other process passing in the parameters to start the script and have it start the script) that will then do the auto-update, via the binding Sergey Grinev mentions--without 'hanging' the Scene/window? Also: Can I then 'stop' this other process if the user requests it?
Here is my current code ('waits' while script--which takes 20-40 min to run!--completes; this is not what I want, I'd like control returned to the user):
public class MyController implements Initializable {
#FXML
private void handleRunScript(ActionEvent event) throws IOException {
ProcessBuilder pb = new ProcessBuilder("myscript.sh", "arg1", "arg2", ...);
Process p = pb.start();
try {
BufferedReader bri = new BufferedReader
(new InputStreamReader(p.getInputStream()));
String line;
while ((line = bri.readLine()) != null) {
System.out.println(line);
textAreaRight.setText(line);
}
bri.close();
p.waitFor();
}
catch (Exception err) {
err.printStackTrace();
}
}
#FXML
private void handleCancel(ActionEvent event) {
doSomethingDifferent();
}
}
To log strings you can use TextArea
To make it asynchronious you need to make a separate thread for output reader.
public class DoTextAreaLog extends Application {
TextArea log = new TextArea();
Process p;
#Override
public void start(Stage stage) {
try {
ProcessBuilder pb = new ProcessBuilder("ping", "stackoverflow.com", "-n", "100");
p = pb.start();
// this thread will read from process without blocking an application
new Thread(new Runnable() {
#Override
public void run() {
try {
//try-with-resources from jdk7, change it back if you use older jdk
try (BufferedReader bri = new BufferedReader(new InputStreamReader(p.getInputStream()))) {
String line;
while ((line = bri.readLine()) != null) {
log(line);
}
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
}).start();
stage.setScene(new Scene(new Group(log), 400, 300));
stage.show();
} catch (IOException ex) {
ex.printStackTrace();
}
}
#Override
public void stop() throws Exception {
super.stop();
// this called on fx app close, you may call it in user action handler
if (p!=null ) {
p.destroy();
}
}
private void log(final String st) {
// we can access fx objects only from fx thread
// so we need to wrap log access into Platform#runLater
Platform.runLater(new Runnable() {
#Override
public void run() {
log.setText(st + "\n" + log.getText());
}
});
}
public static void main(String[] args) {
launch();
}
}

commit fragment from onLoadFinished within activity

I have an activity which loads a data list from the server using loader callbacks. I have to list out the data into a fragment which extends
SherlockListFragment
i tried to commit the fragment using
Fragment newFragment = CategoryFragment.newInstance(mStackLevel,categoryList);
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.simple_fragment, newFragment).commit();
in onLoadFinished and it gives an IllegalStateException saying
java.lang.IllegalStateException: Can not perform this action inside of onLoadFinished
I have referred the example in actionbar sherlock, but those examples have loaders within the fragments and not the activity.
Can anybody help me with this o that I can fix it without calling the loader from the fragment!
Atlast, I have found a solution to this problem. Create a handle setting an empty message and call that handler onLoadFinished(). The code is similar to this.
#Override
public void onLoadFinished(Loader<List<Station>> arg0, List<Station> arg1) {
// do other actions
handler.sendEmptyMessage(2);
}
In the handler,
private Handler handler = new Handler() { // handler for commiting fragment after data is loaded
#Override
public void handleMessage(Message msg) {
if(msg.what == 2) {
Log.d(TAG, "onload finished : handler called. setting the fragment.");
// commit the fragment
}
}
};
The number of fragments depend on the requirement.
This method can be mainly used in case of stackFragments, where all fragments have different related functions.
As per the Android docs on the onLoadFinished() method:
Note that normally an application is not allowed to commit fragment transactions while in this call, since it can happen after an activity's state is saved. See FragmentManager.openTransaction() for further discussion on this.
https://developer.android.com/reference/android/app/LoaderManager.LoaderCallbacks.html#onLoadFinished(android.content.Loader, D)
(Note: copy/paste that link into your browser... StackOverflow is not handling it well..)
So you simply should never load a fragment in that state. If you really don't want to put the Loader in the Fragment, then you need to initialize the fragment in your onCreate() method of the Activity, and then when onLoadFinished occurs, simply call a method on your fragment.
Some rough pseudo code follows:
public class DummyFragment {
public void setData(Object someObject) {
//do stuff
}
public class DummyActivity extends LoaderCallbacks<Object> {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Fragment newFragment = DummyFragment.newInstance();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.simple_fragment, newFragment).commit();
getSupportLoaderManager.initLoader(0, null, this)
}
// put your other LoaderCallbacks here... onCreateLoader() and onLoaderReset()
public void onLoadFinished(Loader<Object> loader, Object result) {
Fragment f = getSupportLoaderManager.findFragmentById(R.id.simple_fragment);
f.setData(result);
}
Obviously, you'd want to use the right object.. and the right loader, and probably define a useful setData() method to update your fragment. But hopefully this will point you in the right direction.
As #kwazi answered this is a bad user experience to call FragmentTransition.commit() from onLoadFinished(). I have found a solution for this event by using ProgressDialog.
First created ProgressDialog.setOnDismissListener(new listener) for watching the onLoadFinished().
Further i do progressDialog.show() before getLoaderManager().restartLoader().
And eventually place progressDialog.dismiss() in onLoadFinished().
Such approach allow do not bind main UI thread and Loader's thread.
public class FrPersonsListAnswer extends Fragment
implements
LoaderCallbacks<Cursor>{
private ProgressDialog progressDialog;
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_persons_list, container, false);
//prepare progress Dialog
progressDialog = new ProgressDialog(curActivity);
progressDialog.setMessage("Wait...");
progressDialog.setIndeterminate(true);
progressDialog.setOnDismissListener(new OnDismissListener() {
#Override
public void onDismiss(DialogInterface dialog) {
//make FragmentTransaction.commit() here;
//but it's recommended to pass control to your Activity
//via an Interface and manage fragments there.
}
});
lv = (ListView) view.findViewById(R.id.lv_out1);
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, final View view,
final int position, long id) {
//START PROGRESS DIALOG HERE
progressDialog.show();
Cursor c = (Cursor) parent.getAdapter().getItem(position);
// create Loader
getLoaderManager().restartLoader(1, null, curFragment);
}
});
return view;
}
#Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
switch (loader.getId()) {
case 1:
//dismiss dialog and call progressDialog.onDismiss() listener
progressDialog.dismiss();
break;
default:
break;
}
}

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